Investigating the vestibular system using modern imaging techniques – A review on the available stimulation and imaging methods

The vestibular organs, located in the inner ear, sense linear and rotational acceleration of the head and itsposition relative to the gravitationalfield of the earth. These signals are essential for many fundamental skillssuch as the coordination of eye and head movements in the three-dimensional space or the bipedal locomotion ofhumans. Furthermore, the vestibular signals have been shown to contribute to higher cognitive functions such asnavigation. As the main aim of the vestibular system is the sensation of motion it is a challenging system to bestudied in combination with modern imaging methods. Over the last years various different methods were usedfor stimulating the vestibular system. These methods range from artificial approaches like galvanic or caloricvestibular stimulation to passive full body accelerations using hexapod motion platforms, or rotatory chairs. Inthefirst section of this review we provide an overview over all methods used in vestibular stimulation incombination with imaging methods (fMRI, PET, E/MEG, fNIRS). The advantages and disadvantages of everymethod are discussed, and we summarize typical settings and parameters used in previous studies. In the secondsection the role of the four imaging techniques are discussed in the context of vestibular research and theirpotential strengths and interactions with the presented stimulation methods are outlined.